1 - hexa-2,4-diyn

Dihydroxy-1,1 -binaphthyl and 1,6-Bis(o-chloropheny 1)-1,6-dipheny 1-hexa-2,4-diyne-l,6-diol, Chem. Lett., 509-512.. 

Almost simultaneously, Sehroth reported that diaeetylene reaets with a hydrazine hydrate solution at 80°C for 4 h to form methylpyrazoles (13) in 80% yield (69ZC108 69ZC110). In the same year, other data eoneeming the reaetion of hydrazine with diaeetylene (65°C, EtOH, yield 65%), hexa-2,4-diyne, and 1,4-diphenylbuta-1,3-diyne were reported (69JOC999). Later, BASF (93GEP4137011) proposed to earry out the proeess at 100°C in a polar solvent with a diaeetylene eoneentration of 14-18% in an inert gas. The yield of methypyrazoles was 90% (post-reetifieation purity 99%). 

The reaction of diacetylene and its asymmetric homologs (penta-l,3-diyne, hexa-1,3-diyne) with semicarbazide (72ZOR2605) affords the amides of 3-methyl-pyrazole- 1-carboxylic acid (27) (80°C, EtONa, EtOH, 40 h). Amide 26 undergoes irreversible rearrangement to amide 27 at 80°C (EtONa, EtOH). 

The reaction of hexa-2,4-diyn-l-al (64) with mercaptoacetaldehyde leads to 2-formyl-5-(prop-l-ynyl)thiophene (65). The addition direction is governed by the aldehyde group via intramolecular aldol condensation in the intermediate (77HOU947). 

The investigation of deprotonated hexa-2,4-diyne [KCH2C C=CCH3 H2C=C=C(K)C=CCH3] has shown (90DIS) that both carbanions are formed. In some cases CS2 reacts with the diyne carbanion to afford 2,5-disubstituted thiophenes 71 (90DIS). 

The thermal solid-to-solid cyclization reaction of diallene derivatives also proceeds stereospecifically. Reaction of 1,6-diphenyl-1,6-di(p-tolyl)hexa-2,4-diyne-l,6-diol (113) with HBr gave meso- (114) and rac-3,4-dibromo-l,6-di-... 

The palladium-catalyzed stannylboration (90) [124] or silylboration (87) [109, 114] succeeds in the intramolecular carbocyclization of diynes and enynes (Scheme 1-27). It is interesting that a very strained four-membered cycUzation of hexa-l,5-diyne proceeds without any difficulties, similarly to five- or six-membered cycUzation. The boryl group is selectively introduced into the more reactive C=CH rather than C=C for enynes and into the terminal C=CH rather than the internal C=CR for diynes, again suggesting a mechanism proceeding through the first insertion into the Pd-B bond in preference to the Pd-Sn or Pd-Si bond. 

Parker, Raphael, and Wilkinson have investigated a synthetic approach to tropinone (124), which they call the acetylenic route (78). Reaction of hexa-1,5-diyne-l,6-dicarboxylate (145) with methylamine yields the pyrrolidine derivative (146), which by catalytic hydrogenation affords the diester 147 (79,50). 

An example illustrating the synthesis of condensed oxepins by the cobalt-catalyzed reaction of bistrimethylsilylacetylene with a hexa-l,5-diyne derivative is shown in Scheme 175.234 This type of process has been discussed earlier in the context of pyran synthesis (see Scheme 158 in Section V,B,2). 

Fig. 16 (a) Comparison of potential energy profile for the formal Cope rearrangement of 3,4-difluorohexa-l,5-diyne-3-ene with that of (Z)-hexa-l,5-diyne-3-ene, (b) Rehybridization in the C(F) bond along the reaction path. EDI = 3,4-difluoro-hex- 3-ene-l,5-diyne ED2 = 1,6-di-fluoro-hex-3-ene-l,5-diyne BZY = difluoro-l,4-didehydrobenzezne TSBC = the transition state for the Bergman cyclization TSRBC = the transition state for the retro Bergman cyclization. 

Reactions of PhC=CC=CPh with iron carbonyls [Fe(CO)s, Fe2(CO)9, or Fe3(CO)i2] give isomers of complexes Fe(CO)4 (diyne)2 (265), Fe2(CO)6 (diyne)2 (266), and Fe2(CO)7 (diyne)2 (267), to which structures analogous to those found for similar products obtained from C2Ph2 were ascribed all three isomers of the second complex were formed. The reactions of hexa-2,4-diyne and Fe(CO)s have been described in more detail. UV irradiation of mixtures of the two... 

Uemura and coworkers discovered another unique rhodium vinylidene-mediated cycloisomerization reaction [11]. They found that in the presence of an electron-rich Rh(I)-complex, [ RhCl(iPr3P)2]2, (Z)-hexa-3-en-l,5-diynes bearing an alkyl substituent at one terminus undergo cycloisomerization to give allylbenzenes (Equation 9.3). 

Radiolysis of the diacetylene hexa-l,5-diyne (50) generates the hexa-1,2,4,5-tetraene radical cation (51 +) via a Cope rearrangement in the Freon matrix. ... 

Keywords 1,6-bis(2,5-dimethoxyphenyl)hexa-2,4-diyne, photopolymerization, diacetylene, polydiacetylene... 

Irradiation of a solution of hexa-/ f -butylcyclotrisilane in the presence of an excess of hexa-2,4-diyne resulted in a smooth reaction leading to a variety of products containing the l,2-disilacyclobut-3-ene ring <19980M1237>. 

Diaminomaleonitrile (178) and l-phenyl-6-(triisopropylsilyl)-hexa-l,5-diyne-3,4-dione (PhC=CCOCOC=CSiPr 3) gave 5- phenylethynyl-6-(triisopropylsilyl)ethynyl-2,3-pyrazinedicarbonitrile (177) (AcOH, 20°C, 5 min 72%)403 the same diamine (178) and 3,3,3-trifluoro-1 -/Molyl-1,2-propanedione (F3CCOCOC6H4Me-p) gave 5-p-tolyl-6-trifluoromethyl-2, 3-pyrazinedicarbonitrile (179) (no details 74%) 807 and the same diamine (178) with / ,//-bis(bromomethyl)benzil (p-BrH2CC6H4COCOC6H4CH2Br-p) gave 5,6-bis[p-(bromomethyl)phenyl]-2,3-pyrazinedicarbonitrile (180)... 

The conversion of an ene-diyne 2.77 into a 1,4-benzenediyl diradical 2.78 on heating is known as the Bergmann reaction . The 1,4-aromatic radical 2.78 maybe converted into benzene or may react with CCI4 to givep-dichlorobenzene (2.79). Bergmann etal converted deuterium-labelled hexa-3-ene-l,5-diyne 2.80 on heating at 200°C into deuterium-labelled hexa-3-ene-l,5-diyne 2.81 in which both deuterium atoms were shifted from the terminal acylene positions to vinyl positions at the interior of the chain. 

The conjugate addition of dithiols to hexa-l,4-diyn-3-ones yields p,P -bis-l,3-dithiane ketones, masked 1,3,5-triketones, which have been converted into dihydro- and tetrahydro-pyrans <03OLl 147>. 

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